The present invention relates to a tape used for COF (chip on film) where a semiconductor element is mounted on a flexible circuit board, and to a semiconductor device formed with the tape for COF.
As a semiconductor device formed with a semiconductor element coupled to and mounted on a flexible circuit board, there has been known a TCP (Tape Carrier Package) semiconductor device. The TCP semiconductor device is provided with an insulating tape having a penetrating opening in which a semiconductor element is mounted, and a tip portion of an wiring pattern is coupled to the semiconductor element in a state that the wiring pattern is protruded like a cartilever. There has been another semiconductor device, as shown in FIG. 15, formed with a semiconductor element coupled to and mounted on a flexible circuit board. In this semiconductor device, a thin film insulating tape 1 does not have a penetrating opening in which a semiconductor element 2 is to be mounted, and a bump 3 of the semiconductor element 2 is coupled to and mounted on an inner lead 4 which is formed on the surface of the thin film insulating tape 1. In addition, reference numeral 5 denotes a sealing resin, and 6 denotes a solder resist. Hereinafter, the latter semiconductor device is referred to as a COF semiconductor device.
In the COF, there is used the thin film insulating tape 1 which has foldability in consideration of its application. Each wire in an wiring pattern disposed on the surface of the thin film insulating tape 1 is electrically connected to a corresponding terminal of the semiconductor element 2, and a connector section for external connection is connected to a liquid-crystal display panel, a printed circuit board and the like. Other exposed portions of the wiring pattern are insulated by a solder resist 6 applied thereon.
In the COF semiconductor device, as shown in FIG. 15, the semiconductor element 2 mounted on the thin film insulating tape 1 is sealed with a sealing resin 5. If air is involved during resin sealing, air bubbles easily generate in the sealing resin since the thin film insulating tape 1 is not provided with an opening in which the semiconductor element 2 is to be mounted. During resin sealing, the sealing resin 5 is applied or injected along each side of the semiconductor element 2. During application of the sealing resin 5 along four sides of the semiconductor element 2, part of air present between the semiconductor element 2 and the thin film insulating tape 1 is sealed as air bubbles in the sealing resin 5. It is difficult to completely prevent air bubbles from being generated in the sealing resin 5.
In the semiconductor device where air bubbles are generated in the sealing resin for the semiconductor element 2, the air bubbles contains moisture and the like which may cause any failure such as inter-terminal leakage.
At present, there are a demand for multiple pins of the COF semiconductor device and another demand for a smaller and thinner COF semiconductor device. In order to fulfill these requests at the same time, it is not only required that a connector section for external connection in an wiring pattern as well as a connection section to a semiconductor element should be more finely pitched, but also it is required that an insulating tape as well as an wiring pattern should be thinner. In order to make a pitch of an inner lead smaller, it is required that to make a width and a thickness of the inner lead smaller.
There are several subjects to be solved in obtaining the fine-pitched and thinner inner lead. One of the subjects is to improve resin sealability (resin filling) of the semiconductor element. Particularly, the fine-etched and thinner inner lead makes it more difficult to remove air bubbles, which are generated during resin sealing of a semiconductor element, from the sealing resin. Therefore, it is required in the fine-pitched and thinner inner lead to prevent air bubbles from being generated.
As a countermeasure against generation of air bubbles, an opening is provided in the thin film insulating tape as is the case with the above-stated TCP semiconductor device. Another countermeasure is shown in FIG. 16 (FIG. 15 is a cross sectional view taken in the line A-Axe2x80x2 of FIG. 16). In FIG. 16, resin is applied along three sides shown with an arrow B or only one side shown with an arrow C of the semiconductor element 2. Air present in a resin application region before resin application is removed through a non resin application region to the air.
However, the above-stared conventional countermeasures against air bubbles in the COF semiconductor devices have following subjects.
In the case of she former countermeasure where an opening is provided in the thin film insulating tape, sealing resin overflows from the opening of the thin film insulating tape to a lower part Thereof during the process of resin sealing. The overflowed sealing resin adheres to a stage, which leads to any manufacturing failure. In addition, the thus-manufactured COF semiconductor devices result in becoming thicker, which is against the recent demand for thinner semiconductor devices.
In the case of the latter countermeasure where resin is applied along three sides or only one side of the semiconductor element 2 as shown in FIG. 16, the sealing resin 5 flows at a higher velocity from a corner of the semiconductor element 2, where an interval between inner leads becomes wider, to a space between the semiconductor element 2 and the insulating tape. This may result in taking air in the resin to generate air bubbles.
In addition, if the COF semiconductor device after installation is used in a temperature cycling environment where a low temperature and a high temperature are alternately repeated, thermal expansion and contraction are repeated due to the temperature cycling. Accordingly, due to difference in thermal expansion coefficient of materials, stress is generated around an edge of a solder resist opening which is provided for establishing electrical connection between the inner leads and the semiconductor element, which may cause disconnection of the inner leads.
Another problem involved in implementing a fine-pitched and thinner inner lead is that inner leads around the edge of the solder resist opening may be more remarkably disconnected in the temperature cycling because mechanical strength of the inner leads is decreased as a result of making the inner lead thinner. Therefore, for making the inner leads of the COF semiconductor device fine-pitched and thinner, mechanical strength of the inner lead section around the edge of the solder resist opening should be improved, which indicates that implementation of the fine-pitched device is difficult in the current state,
It is an object of the present invention to provide a tape for COF and a semiconductor device therewith, which tape is capable of preventing air bubbles from being generated during resin sealing of a semiconductor element and capable of decreasing disconnection of an inner lead located at a corner of the semiconductor element.
In order to accomplish the above object, a first aspect of the present invention provides a tape for chip on film on which a semiconductor element is mounted and resin is applied for sealing the semiconductor element, the tape for chip on film comprising:
an insulating tape;
a plurality of wiring patterns formed on the insulating tape;
a solder resist partially covering the wiring patterns by application to have an opening; and
a dummy pattern provided at a corner of a region for the semiconductor element to be mounted so as to control flow of the resin from the corner to a space between a surface of the semiconductor element and the insulating tape during resin sealing.
The tape for chip on film according to the above constitution decreases a flow velocity of the resin flowing from the corner to the space between the surface of the semiconductor element and the insulating tape, which reduces air taken in the resin caused by the resin flow, resulting in prevention of air bubble generation.
In an embodiment of the first aspect of the present invention, the dummy pattern is provided inside the opening of the solder resist and inside or outside the corner, and a shape of the dummy pattern is formed along a shape of the corner.
According to the above constitution, the thickness of the dummy pattern can be larger than the space between the semiconductor element and the insulating tape when the dummy pattern is provided outside the corner in particular, which effectively reduces flow of the sealing resin to the space between the surface of the semiconductor element and the insulating tape during resin sealing.
In an embodiment of the first aspect of the present invention, the dummy pattern is provided from outside or inside the corner to the solder resist.
According to the above constitution, the dummy pattern is connected with the solder resist. Therefore, the dummy pattern can absorb part of stress generated due to repeated thermal expansion and contraction around the opening edge of the solder resist, which decreases stress put on the inner lead located at the corner. As a result, disconnection of the inner lead can be prevented.
In an embodiment of the first aspect of the present invention, the dummy pattern is composed of a large width section of an inner lead of a wiring pattern inside the opening of the solder resist.
The large width section of the inner lead also controls flow of the resin from the corner to the space between the semiconductor element and the Insulating tape during resin sealing.
In an embodiment of the first aspect of the present invention, the dummy pattern is provided at least at two adjacent corners of the region for the semiconductor element to be mounted.
It is possible to prevent air from being taken in the resin at the two adjacent corners during application of sealing resin since the dummy pattern is disposed at the two adjacent corners.
In an embodiment of the first aspect of the present invention, material and thickness of the dummy pattern is the same as those of the inner lead.
According to the above constitution, the dummy pattern can be formed at the same time when the wiring patterns are formed, which saves an additional process and material for forming the dummy pattern.
A second aspect of the present invention provides a tape for chip on film on which a semiconductor element is mounted and resin is applied for sealing the semiconductor element, the tape for chip on film comprising:
an insulating tape;
a plurality of wiring patterns formed on the insulating tape; and
a solder resist partially covering the wiring patterns by application to have an opening, wherein
an opening edge of the solder resist opposed to a corner of a region for the semiconductor element to be mounted is located in a vicinity of the corner, and a shape of the opening edge of the solder resist in the vicinity of the corner is made along a shape of the corner so as to control flow of resin from the corner to a space between a surface of the semiconductor element and the insulating tape during resin sealing.
According to the above constitution, the solder resist opposed to the corner of the region for the semiconductor element to be mounted is made near and along the corner. Therefore, the solder resist controls the flow rate of resin from the corner to the space between the surface of the semiconductor element and the insulating tape during resin sealing. This results in prevention of air bubble generation.
A third aspect of the present invention provides a tape for chip on film on which a semiconductor element is mounted and resin is applied for sealing the semiconductor element, the tape for chip on film comprising:
an insulating tape;
a plurality of wiring patterns formed on the insulating tape;
a solder resist partially covering the wiring patterns by application to have an opening; and
an inner lead in a wiring pattern located on a specified side of a region for the semiconductor element to be mounted inside the opening of the solder resist, wherein
the inner lead has a large width section wider than an electric connection section of the inner lead connected to the semiconductor element so as to control flow of resin from the specified side to a space between a surface of the semiconductor element and the insulating tape during resin sealing.
According to the above constitution, the large width section of the inner lead on the specified side of the region for the semiconductor element to be mounted decreases a flow velocity of the resin flowing from the specified side to the space between the surface of the semiconductor element and the insulating tape, which reduces air taken in the resin caused by the resin flow, resulting in prevention of air bubble generation.
In an embodiment of the third aspect of the present invention, the large width section of the inner lead is disposed either outside or inside a border line of the region for the semiconductor element to be mounted, or from outside to inside the border line of the region.
According to the above constitution, the large width section of the inner lead controls flow of resin from the border line of the region for the semiconductor element to be mounted to the space between the semiconductor element and the insulating tape during resin sealing.
In an embodiment of the third aspect of the present invention, the large width section of the inner lead is disposed from outside or inside a border line of the region for the semiconductor element to be mounted to inside a region for the solder resist to be applied.
According to the above constitution, the large width section of the inner lead not only controls flow of resin, but also improves mechanical strength of the inner lead because the large width section of the inner lead is disposed inside the solder resist. This increases disconnection of the inner lead caused by stress that is generated in the vicinity of the opening edge of the solder resist due to repeated thermal expansion and contraction.
In an embodiment of the third aspect of the present invention, there is proved the tape for chip on film, further comprising:
a dummy pattern provided at a corner of a region for the semiconductor element to be mounted so as to control flow of the resin from the corner to a space between a surface of the semiconductor element and the insulating tape during resin sealing.
In an embodiment of the third aspect of the present invention, an opening edge of the solder resist opposed to a corner of a region for the semiconductor element to be mounted is located in a vicinity of the corner, and a shape of the opening edge of the solder resist in the vicinity of the corner is made along a shape of the corner so as to control flow of resin from the corner to a space between a surface of the semiconductor element and the insulating tape during resin sealing.
In an embodiment of the second aspect of the present invention, there is proved the tape for chip on film, further comprising:
a dummy pattern provided at a corner of a region for the semiconductor element to be mounted so as to control flow of the resin from the corner to a space between a surface of the semiconductor element and the insulating tape during resin sealing.
According to the above three embodiments based on combination between the fist, second and third aspect of the present invention, there are obtained such synergical effects as described in the fist, second and third aspect of the present invention.
In an embodiment of the third aspect of the present invention, the wiring pattern, the inner lead, and the dummy pattern are fixed to the insulating tape without use of an adhesive.
In an embodiment of the third aspect of the present invention, the wiring pattern, the inner lead, and the dummy pattern are fixed to he insulating tape with use of an adhesive.
A fourth aspect of the present invention provides a semiconductor device comprising a semiconductor element mounted on the tape for chip on film as described above.
According to the above semiconductor device, air bubbles generated during sealing of the semiconductor element with resin are eliminated. This prevents such a failure as inter-terminal leakage caused by moisture and the like contained in the air bubbles.